Shock absorbers



O 1951 c. M. L. BOURCIER DE CARBON 3,003,596

SHOCK ABSORBERS Original Filed Feb. 21, 1955 5 Sheets-Sheet l INVENTORATTORNEYS Oct. 10, 1961 c. M. BOURCIER DE CARBON 3, 3,5 6

SHOCK ABSORBERS Original Filed Feb. 21, 1955 3 Sheets-Sheet 2 ATTORNEYSOct. 10, 1961 C. M. L. L. BOURCIER DE CARBON SHOCK ABSORBERS 3Sheets-Sheet 3 Original Filed Feb. 21, 1955 ATTORNEYS 3,903,595 PatentedOct. 10, 196i SHOQK ABSORBERS Christian Marie Lucien Louis Bourcier tleQarhon, 64 Blvd. Maurice-Barres, Neuilly-snr-Seine, France Originalapplication Feb. 21, 1955, Ser. No. 489,694.

Divided and this application Mar. 11, 1959, Ser; No. 798,707

6 Claims. (Ci. res-as This invention relates to shock absorbers and moreparticularly to shock absorbers of the fluiddisplacement type adaptedespecially for use on automotive vehicles, although capable ofemployment in cushioning or braking shocks sustained by other devicesand mechanisms.

This application is a division of my copending application Serial No.489,694, filed February 21, 1955, and now forfeited; which applicationis a continuation-inpart of my application Serial No. 230,944, filedJune 11, 1951, now patent No. 2,748,898.

More particularly the invention relates to improvements in pistons usedin such hydraulic devices, which pistons are provided With passagewaysleading from one side to the other thereof, the passageways beingcontrolled by disc or flap valves usually consisting of a thin resilientsheet of metal or other suitable material.

It is the general. object of the present invention to provide a noveland improved shock absorber piston in which the curve of shock absorberresistance as a function of the piston velocity is approximately astraight line. More specifically, it is an object of the invention toattain a construction and operation of the piston by providing novelvalving arrangements which control the by-passing of fluid from one sideof the piston to the other during operation so that the aforesaid objectof the invention in straightening theresistance-velocity curve may beattained.

Other objects and features of novelty will be apparent from thefollowing specification when read in connec tion with the accompanyingdrawings in which certain embodiments of the invention are illustratedby way of example.

In the drawings:

FIGURE 1 is a graph in which certain characteristics of the shockabsorber of this general type are indicated by curves, and in which theresistance R of the damping is shown as a function of piston velocity V;

FIGURE 2 is a fragmentary vertical sectional view through the valvedorifice portion of a by-pass passageway through the piston of a shockabsorber embodying the principles of my invention; the relationship ofthis orifice to the other parts of the piston being readily apparentfrom a comparison with FIGURE 6, described below;

FIGURE 3 is a diagrammatic plan View of the orifice valve arrangementshown in FIGURE 2;

FIGURE 4 is a view similar to FIGURE 2 showing a modification of theorifice valving;

FIGURE 5 is a fragmentary plan view of the orifice shown in FIGURE 4;

FIGURE 5A is a fragmentary View similar to FIG- URE 4 showing a slightlymodified form of orifice;

FIGURE 6 is a vertical sectional view of a shock absorber pistonillustrating a still further modification of the valving provisions;

FIGURE 7 is a top plan view of the piston shown in FIGURE 6, with aportion of the valving broken away to better illustrate the constructionof the piston body;

FIGURES 8, 9 and 10 are views similar to FIGURE 6 showing a modifiedmultiple-orifice piston in three respective conditions of operationduring the compression stroke of the piston;

FIGURE 1 1 is a similar view showing a condition of minimum opening ofthe valving on the rebound stroke;

FIGURE 12 is a top plan view of the piston shown in FIGURES 8-11; and

FIGURE 13 is a bottom plan view of that piston.

In order to obtain the best possible clamping, particularly in the caseof shock absorbers for land vehicles, it is preferable that the curve ofthe resistance R of the shock absorber, as a function of the speed V ofthe piston thereof, be as near a straight line as possible. It has beenfound that this curve, in the case of pistons of the generalconstruction of that shown in my aforesaid patent No. 2,748,898 (thatis, where the sheet or disc valves seat upon an orifice opening out of aplane surface) has the shape indicated at A in the graph comprisingFIGURE 1 of the present drawings.

In other words, a substantial viscous resistance opposes the flow of oilduring operation so long as the valves are not raised or opened aconsiderable amount, say a distance of the order of magnitude of a fewtenths of a millimeter. The hydraulic force necessary to open the valvesto this initial extent is equivalent in practice to a resistance whichwould be encountered by very small movements of the piston as duringtravel of the vehicle on a relatively smooth paved street or boulevard,and this makes such boulevard riding less smooth than should beexpected.

The improvements which are the subject of the present invention aredirected primarily at bringing the said curve A as close to the straightline indicated at B in the graph, as possible.

One way of initiating this conformation of the curve A would be to addother passageways through the piston which are not controlled by thevalving provisions. The presence of such passageways and orifices tendsto flatten the curve near the origin, but without having any practicalefiect beyond this.

Secondly, one may proceed by combating this phenomenon at its source byseeking to decrease the constant visoscity resistance to flow throughthe valve, by seeing to it that the streams of liquid through theorifices are made laminar or flattened over the smallest possible lengthof their course, say for example, for a distance not substantially morethan approximately 1 mm.

This result can be obtained in various ways, particularly by thefollowing means which may be applied either separately or one incombination with any or all of the others;

(a) The thin sheet which constitutes the resilient disc valve may be socut that its peripheral edge is practically tangential to the margin ofthe orifice, so that the covering of theorifice is at a minimum (such asin my Patent No. 2,748,898);

([2) The seat surrounding the orifice against which the valve closes maybe made extremely thin or narrow rather than with a wide supportingsurface for the valve, at least over a part of the periphery thereof.For example, the valve seat may be provided in the general shape of theedges of a crater of a volcano (see also, for example, my Patent No.2,815,100, granted December 3, 1957);

(c) This effect may probably best be attained by providing a valvingconstruction whereby the orifice controlled by the disc valve ispermanently open to an exceedingly small extent. This result can beobtained in a number of dilferent ways, as will be seen from aninspection of FIGURES 2-6 of the drawings. A general inspection of thesefigures reveals that the effect may be attained, first by arranging theperiphery of the disc valve a little short of tangency with theperiphery of the orifice thus leaving a very small space between theseperipheries as at 8 in FIGURES 2 and 3; the edge of the orifice may bebevelled or chamfered off as on the secant plane X-X in FIGURES 4 and 5;this bevelling or chamfering may be effected along a curved line assuggested at y in FIGURE 5A; or the disc valving may be initially spaceda small distance from the orifice of the passageway, throughout theperiphery of the orifice, as indicated in FIGURE 6.

For purposes of convenience, it might be well to describe in detail theembodiments shown in FIGURES 6 and 7 first since they, althoughfragmentary in execution, show the mounting of the piston on the pistonrod and the fitting of the piston to the walls of the shock absorbercylinder. The piston rod is provided with narrowed or attenuated endportion 12, the extreme end of which is provided with screw threads uponwhich is adapted to be screwed the retaining nut 15. Just above theshoulder at the base of the portion 12 and just below the nut 15, thereare disposed retaining washers or discs 13 which fit snugly around thepiston rod stem 12 and enclose between themselves the piston and valvingstructure.

The central portion 14 of the piston is circular in transverse sectionand fits snugly within the cylindrical walls of the shock absorbercylinder as clearly shown in FIG- URE 6. Somewhat along the lines of thepiston illustrated in my Patent No. 2,748,898, a basically oblong raisedportion is formed on the upper surface of the midportion 14 and extendsfrom right to left of FIGURES 6 and 7 and is designated 14A. A similaroblong boss designated 14B is formed on the underside of theintermediate portion 14 of the piston and extends at right angles to thetop boss. In this example, two pairs of fluid passageways extend throughthe piston, two of the passageways passing through the intermediateportion 14 and the upper extended oblong portion 14A, these being shownin FIGURE 6, and two of them passing through the intermediate portion 14and the lower oblong boss 14B as shown at the top and bottom portions ofFIGURE 7. The passageways shown in FIGURE 6 are the rebound passagewaysand their orifices opening out through an annular frusto-conical orcrater-like boss formed in the portion 14A are adapted to be controlledby the stack of valving discs 9, it and 11 shown at the top of FIG- URE6. Any desired number of these discs may be employed depending upon thequalities of the shock absorber desired, and they are preferably ofgraduated diameters, the larger disc of course nearest the orifices.

The opposite passageways 1, those shown at the top and bottom of FIGURE7, are compression orifices and open downwardly through similarcone-like or crater-like orifices which are controlled by the lower setsof valve discs 9, and 11.

In order to maintain the initial planar position of the valve discs, andto protect them against fatigue and breakage and to prevent reversebending, pedestals or supports 17 are provided, these supports occurringin pairs which are spaced at approximately 90 from the mouth of theorifices upon the same side of the piston. For example, the pedestal 17disclosed in solid lines at the bottom of FIGURE 7 tends to limit theclosing of the valve discs which control the upper orifice of thepassageway 1 which occurs at the left side of FIGURE 7; whereas thepedestals 17 which occur at both side portions of FIGURES 6 and 7 (shownin solid lines in FIGURE 6 and dotted lines in FIGURE 7) serve to limitthe closed position of the lower set of valves 9, 1t? and 11 whichcontrol the orifices of the openings at the top and bottom of FIGURE 7.In their limited minimum opening positions the valves are spaced a veryslight distance, of the ordered magnitude of say a few tenths of amillimeter, away from the mouth of the orifices as clearly shown in thevalving illustrated in the upper portion of FIGURE 6.

A circular boss 16 is provided on the oblong upper and lower bosses 14Aand 14B, the upper one of these bosses being clearly shown in FIGURES 6and 7 at 16, and the sets of valve discs are clamped between thecircular bosses and the respective retaining plates or washers 13. Inthis Way, the stack of resilient discs is given great rigidity in itscentral portion while retaining flexibility in its peripheral portion.

Another means for attaining the desired solution of the problem is theone illustrated in FIGURES 4 and 5 of the drawings in which the conicalcrater of the orifice of the passageway 1a is chamfered or bevelled oil?on a diagonal plane x-x and this affords a preliminary or initialadditional opening of the orifice as indicated at f. The angle ofinclination of the plane x-x which modifies the seat of the valve maypreferably lie between about 3 to about 10 with respect to thehorizontal. In this case the initial spacing of the valve disc, shown at6a in FIGURE 4, can be provided also, as in the case of the previouslydescribed embodiment. Further, it is possible for the valve 6a, duringopposite movement of the piston, to conform itself somewhat to thebevelled surface of the orifice to effect closure thereof. This closingeffect on reverse stroke may be more readily attained in the embodimentillustrated in FIGURE 5A where the bevelling is along a rounded orgently curved substantially spherical surface y. The minute free passageof oil at f has the result of offering a certain cross-section ofopening even before the disc valve has begun to open.

Another solution which can be combined with any one of the previouslydescribed embodiments consists of causing the valve disc 6 to closesomewhat short of the outer marginal portion 7 of the orifice 1, asillustrated in FIG- URES 2 and 3. In other words, the periphery of thevalve disc 6 is positioned inwardly of the point of tangency with theperiphery 7 of the orifice, thus leaving a small cusp-like opening orcrack 8 through which the damping fluid may pass.

It is also within the scope of the invention to use in any of theembodiments, either a single disc valve as shown in FIGURES 2-5Ainclusive or multiple graduated sheets of foil of decreasing dimensionsas shown in FIGURES 6 and 7.

Referring back again to FIGURE 1 0f the drawings, it can be seen thatthe curve A of resistance of the shock absorber as a function of thespeed V of the piston has near its origin a portion a which is quite faraway from the strai ht line B. The explanation of this shape of thecurve is that the flow of the damping liquid when the valve consists ofa sheet of foil, and when the seat of the valve is a broad flat surface,is opposed (in the case of very small lifting motions) by substantialviscous resistance or stickiness. In order that the flow become normaland of any substantial degree, it is necessary that the valve foil ordisc be raised several tenths of a millimeter. Due to these phenomena,furthermore, the temperature variations which exert an influence on theviscosity of the liquid, modify the operation of theshock absorber.

These phenomena are all the more important the more viscous the liquid(for example oil) used as the damping medium in the shock absorber. Nowit is preferable to use a viscous liquid in these shock absorbers forother reasons, in particular to decrease the possibility of leakagebetween the piston and the cylinder and to avoid the harmful influenceof any possible lack of precision in the production of the tubes orcylinders and pistons.

The applicant has found that it is possible to overcome this drawback toa certain degree by imparting to the valve seat about the piston orificesuch a shape that the contact of the valve disc does not take placealong a wide flat surface, but along a narrow annular seating which isas close to line contact as is practicable. This feature is clearlyshown in FIGURE 2 of the drawings in which the orifice in general is ofa cone-like configuration 5 having an outer frusto-conical surface 3 andthe actual seating of the valve taking place along the lip 4, theextremely narrow dimension e of which is reduced as much as possiblewith due regard to the strength of the materials used. In the case ofpistons J made of alloys such as that known as Zamak (which is aZinc-base, die-casting alloy containing approximately 4% of aluminum,approximately 0.04% of magnesium, and from zero to approximately 1.0% ofcopper), and a valve of sheet steel, the value of e for an orifice 1having a diameter of approximately 7 mm., may advantageously be betweenabout 0.3 and about 1 mm. Of course, the actual profile of the Orificerim could be varied from that shown provided that the supporting area.is reduced as just described.

In straightening the part b of the curve A to bring it more in line withthe straight line B, the diameters of the orifices of the passagewaythrough which the damping liquid moves from one side of the piston tothe other, should be selected properly. The resistance to the flow ofthe oil through the passageway orifices themselves is of course added toa certain extent to the resistance to the flow of oil between the valvesand their seats. This resistance to fiow through the passageway orificesthemselves can therefore be controlled to straighten the portion [2 ofthe curve A and bring it closer to the straight line B. It is thereforeone factor of the present invention to not only select an approximateoptimum crosssection of the passage openings but also, and this is veryimportant, the variation of this optimum cross-section as a function ofthe reduction ratio r between the stroke of the wheel with respect tothe frame and the stroke of the piston in the shock absorber cylinder.In the event that the orifices of the piston consist of two groups ofcylindrical ports, the applicant has discovered that the optimumdiameter d of the orifices, given in millimeters, is approximatelyaccording to the following equation:

in which D is the inner diameter of the cylinder, also in millimeters.For a cylinder of the diameter of 46 mm. this corresponds to an optimumdiameter of the orifices of 9 mm. when the value of r is close to 1(which condition frequently occurs in connection with the rear shockabsorbers of present-day automobiles), and corresponds to an optimumdiameter of 5.5 mm. when the value of r is close to 2. (frequently thecase in front shock absorbers of present-day automobiles).

This value of the diameter of the orifices (or of the equivalent area inthe case of non-circular orifices or in the case of a difierent numberof orifices) can vary about 20% up or down with respect to the optimumvalue given by the above formula, without going beyond the scope of thepresent invention.

Under these conditions, in the case of shock absorbers for land vehiclesin accordance with the present invention, the diameters of thepassageway openings in the pistons of the front and rear shock absorbersmay differ for one and the same vehicle, this being contrary to theusual practice up to the present time in the case of hydraulic shockabsorbers employing valved pistons.

In FIGURES 813 inclusive there is illustrated another embodiment of theinvention in which more passageways are provided through the piston thanin the earlier described embodiments and which involve other minorchanges of construction. In these figures, the narrowed or attenuatedportion of the piston rod is represented as in the other figures by thenumeral 12 and the piston body 20 is clamped upon the end of the rod bymeans of the nut 15 and the intervening upper and lower washers 13'. Inthis case the washers 13 have rounded edges. Clamped between the upperand lower surfaces of the piston and the respective washers 13' are therelatively thin and flexible disc valves 21 and the reinforcing orstiffening disc 22 at the upper side and the resilient valve disc 24 andreinforcing disc 25 at the lower side.

In all, there are sixteen passageways passing through 6 the piston fromthe upper surface to the lowersurface thereof and a reference to FIGURESl2 and 13 of the drawings will reveal the allocation of thesepassageways to flow during the compression stroke and during the reboundstroke of the piston.

Referring now to FIGURE 12, which is a plan view of the top surface ofthe piston, it will be seen that the passageways are arranged in pairsand that the pairs of passageways 30, 6-1, 32 and 33 open out upon theupper surface through a plurality of raised bosses 35, the uppersurfaces of these bosses being co-planar with the central boss 36 of thepiston which directly underlies the valving provisions. It will beunderstood that the intervening surfaces of the piston 20 indicated at37 occupy a slightly lower plane.

Also provided on the upper general surface of the piston 20 are theledges or pedestals 39 which serve to give steadying and protectingsupport to the valving discs adjacent areas remote from the nozzles ororifices which are valved at the upper surface of the piston. Thesepedestals 39 also prevent the valve from coming too close to thepassageways providing flow in the opposite direction through the piston.

Reference to FIGURE 11 of the drawings Will clearly show how the valvedisc 21 closes upon the orifices of the passageways 30, 31, 32 and 33which control the rebound flow through the piston.

Referring now to FIGURE 13 of the drawings, it will be seen that therebound passageways 3t 31, 32, 33 open out through the depressed lowersurface at of the lower face of the piston which is at a lower levelthan the central boss. 41 and the pedestals 42 which surround theorifices of the compression passageways 45, 46, 47 and 48. In FIGURES 8,9 and 10 the operation of the valve discs 25 against the orifices ofthese passageways is clearly shown. Pedestals 50 are provided on thelower surface of the piston and serve the same purpose in connectionwith the valving 25 as the upper pedestals 39 serve in connection withthe valve disc 21.

In accordance with one of the main principles of the present invention,the orifices of the various passageways which open out through thebosses 35 and 42 are bevelled off as at 55 so that for the minimumopening operating conditions (shown in FIGURE 8 for the compressionvalving) the valving 25 will be cracked or slightly open to the extentafforded by the bevelling of the orifice. The degree of bevel is greatlyexaggerated in the drawings for purposes of clarity of illustration andit is to be understood that the depth of the bevelled edge is in theorder of magnitude of a few tenths of a millimeter.

Under conditions of greater pressure and piston velocity during thecompression stroke, the valve 25 will open further as, for example, asillustrated in FIGURE 9 of the drawings. Then, for perhaps the maximumopening during compression for a fairly rough road, the condition wouldbe as illustrated in FIGURE 10.

Further with reference to the last described embodiment of theinvention, it is to be observed that the provision of the multiplicityof passageways (16 in the illustrated embodiment) serves to distributethe load on the valve discs throughout a greater portionof theirperiphery. In fact, according to this embodiment, the damping oil reactsagainst approximately from to of the valve disc circumference on eachside thereof, or a total of from about to For a given total orificearea, distribution of the pressure over a Wider arc of the discs servesto reduce the amount of flexing which must take place, with a consequentincrease in valve disc life. Also, the arrangement of the arcuateorifices or groups of orifices upon diametrically opposite sides of theinstallation causes the disc valves to flex cylindrically rather thanconically and this makes for better operation and prolonging the life ofthe discs. I

There are a number of factors with regard to this piston valvingarrangement which serve to prolong the life of the valve discs: theaforesaid distribution of the pressure over a. larger area; thepreliminary by-passing of the oil which eliminates the need for thevalves to flex during low velocity strokes, or at the beginning of highvelocity strokes; the radius provided on the retaining nut and washerwhich allows the disc to flex naturally around the edge of the washer ornut; the large diameter of the discs which are. employed, the discsbeing almost as large as the piston itself, thus providing a longbending moment arm; and the provision of laminated construction of thediscs where a plurality of discs of various diameters are stacked, thuspreventing over-flexing and permitting the development of suflicientholding power without resorting to excessively thick discs.

It should also be borne in mind that, since the holes or openings arearranged in opposed groups the valve discs are not flexed in a trulyconical manner, but tend to flex cylindrically, as in the case of thearrangement described in my Patent No. 2,748,898. It is also to be notedthat the valve discs are normally in a relaxed state and not pre-loadedas in the case of conventional shock absorbers of this general type.

Another advantage of the provision of the large number of openingsemployed in the last described embodiment of the invention may bementioned. One suggested range of thickness of the valve discs for thesepurposes is from about 0.008 to about 0.018. The use of muitiple discsof approximately this range of thickness in connection with the largenumber of openings used affords a great degree of control of the shockabsorber action. If only two holes or openings of considerable diameterwere used, instead of the present suggested arcuate orifice arrangement,extremely heavy discs would be required to prevent gushing and severeand excessive deflection.

It is understood that various changes and alterations may be made in theembodiments illustrated and described herein without departing from thescope of the invention as defined by the following claims.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

l. A double acting shock absorber of the class described, comprising acylinder containing a working fluid, a single working piston containedtherein and adapted to reciprocate within said cylinder and to have itsmovements damped by means of said fluid, and a solid piston rod fixed tosaid piston and extending through an opening in one end of the cylinder,said piston being the only piston device carried by said piston rod;said piston provided with two sets of passageways therethrough throughwhich fluid may pass from one side of the piston to the other duringworking movement of the piston, one of said sets of passageways servingto transmit fluid in one direction through the piston and anotherdifferent set of said passageways serving to transmit fluid in theopposite direction therethrough, and valve means controlling the flow offluid in said respective sets of passageways; said respective sets ofpassageways for transmitting fluid in the two opposite directions beingthe only means for bypassing working fluid from one side of the pistonto the other, said sets each arranged in only two groups of at least onepassageway each, the groups of each set being positioned exactlydiametrically opposite each other on opposite sides of the axis of thepiston, and the groups of the set for flow in one direction being spaced90 from the adjacent groups of the set for flow in the oppositedirection, the passageways of said sets having inlet and outlet orificeson the respective sides of the piston; said valve means comprising atleast one completely circular flat resilient leaf element securedfixedly adjacent its center to the central portion of one face of thepiston, and at least one completely circular flat resilient leaf elementsecured fixedly adjacent its center to the central portion of theopposite face of the piston; said circular leaf elements beingimperforate except for its axial central securing point, the leafelements on each side of the piston adapted to extend over andresiliently control the flow of working fluid from the outlet orificesof the sets of passageways debouching on its respective side of thepiston, and the inlet orifices of the other set of passageways on thatside of the piston being spaced away from said circular leaf element soas not to be controlled thereby; the said outlet orifices beingsubstantially in the plane of the leaf element which controls them andopening individually through the surface of the piston whereby flowthrough the respective passageways is individually controlled, theoutlet orifices of the respective passageways for transmitting fluid inthe same direction being disposed beneath diametrically oppositeportions of the respective eaf elements at points remote from the axisthereof so that the leaf elements are stressed and resiliently bent onlyin a simple substantially cylindrical configuration by fluid issuingunder pressure from the openings which they cover.

2. A double acting shock absorber of the class described, comprising acylinder containing a working fluid, a single working piston containedtherein and adapted to reciprocate within said cylinder and to have itsmovements damped by means of said fluid, and a solid piston rod fixed tosaid piston and extending through an opening in one end of the cylinder,said piston being the only piston device carried by said piston rod;said piston provided with two sets of passageways therethrough throughwhich fluid may pass from one side of the piston to the other duringworking movement of the piston, one of said sets of passageways servingto transmit fluid in one direction through the piston and anotherdifferent set of said passageways serving to transmit fluid in theopposite direction therethrough, and valve means controlling the flow offluid in said respective sets of passageways; said respective sets ofpassageways for transmitting fluid in the two opposite directions beingthe only means for bypassing working fluid from one side of the pistonto the other, said sets each arranged in only two groups of at least onepassageway each, the groups of each set being positioned exactlydiametrically opposite each other on opposite sides of the axis of thepiston, and the groups of the set for flow in one direction being spacedfrom the adjacent groups of the set for flow in the opposite direction,the passageways of said sets having inlet and outlet orifices on therespective sides of the piston, said valve means comprising at least onecompletely circular ilat resilient leaf element secured fixedly adjacentits center to the central portion of one face of the piston, "and atleast one completely circular flat resilient leaf element securedfixedly adjacent its center to the central portion of the opposite faceof the piston; the leaf elements on each side of the piston adapted toextend over and resiliently control the flow of working fluid from theoutlet orifices of the sets of passageways debouching on its respectiveside of the piston, and the inlet orifices of the other set ofpassageways on that side of the piston being spaced away from saidcircular leaf element so as not to be controlled thereby; the saidoutlet orifices being substantially in the plane of the leaf elementwhich controls them and opening individually through the surface of thepiston whereby flow through the respective passageways is individuallycontrolled, the outlet orifices of the respective passageways fortransmitting fluid in the same direction being disposed beneathdiametrically opposite portions of the respective leaf elements atpoints remote from the axis thereof so that the leaf elements arestressed and resiliently bent only in a simple substantially cylindricalconfiguration by fluid issuing under pressure from the openings whichthey cover, the controlled outlet orifices of the passageways debouchingfrom the piston surface toward the leaf element which controls it,through a raised boss the top of which provides a narrow annular seatingsurface for said leaf element, and said annular seating surfaces aroundthe respective orifices being ohamfered radially outwardly so as toprovide a permanently open slit for each passageway.

3. The shock absorber as set forth in claim 2 in which the chamfer ofthe orifice seating surfaces is on a gently curved contour.

4. The shock absorber as described in claim 1 in which each group ofpassageways assumes an arcuate configuration with its center ofcurvature at the axis of the piston, whereby the respective valve leafelements controlling compression and rebound action are subjected topassageway pressures over a considerable are upon diametrically oppositesides of the leaf elements, which causes the leaf elements to flexcylindrically rather than conically and the pressure to be distributedaround the leaf elements, all of which has the eifect of preventingfatigue and diminishing the wear on the said leaf elements.

5. A double acting shock absorber of the class described, comprising acylinder containing a working fluid, a piston contained therein andadapted to reciprocate Within said cylinder and to have its movementsdamped by means of said fluid, and a piston rod fixed to said piston andextending through an opening in one end of the cylinder; said pistonprovided with passageways therethrough through which fluid may pass fromone side of the piston to the other during working movement of thepiston, certain of said passageways serving to transmit fluid in onedirection through the piston and other of said passageways serving totransmit fluid in the opposite direction, and valve means controllingthe selective flow of fluid in said respective passageways; saidpassageways being arranged so that the first named passageways for flowin said one direction are circumferentially spaced from the second namedpassageways for flow in the opposite direction, said respectivepassageways for transmitting fluid in the two opposite directions eachbeing arranged in two groups of at least one orifice each, said groupspositioned exactly diametrically opposite each other on opposite sidesof the piston, said valves comprising at least one flat resilient leafelement secured to the intermediate portion of one face of the pistonand at least one fiat resilient leaf element secured to the intermediateportion of the opposite face of the piston, said leaf elements adaptedin repose to extend over the respective outlet orifices of therespective passageways which they control and to be spaced remotely fromthe inlet orifices of the other passageways, the outlet orifices of therespective passageways for transmitting fluid in the same directionbeing disposed beneath diametrically opposite portions of saidrespective leaf elements at points remote from the axis thereof so thatthe leaf elements are stressed and resiliently bent only in a simplesubstantially cylindrical configuration by fluid issuing under pressurefrom the openings which they cover; the respective faces of the pistonhaving flat plane surfaces in two axially spaced levels, the passagewaysfor flow of fluid in one direction having their inlet orifices on oneface of the piston at a level axially inset from the level of saidsurface in which the outlet orifices of the other passageways areformed; and the valve leaf elements being secured to the respectivepiston faces approximately at the outer levels, whereby they control theoutlet orifices of the appropriate passageways and lie in planes spacedaxially from the plane of the inlet orifices of the other passageways.

6. The shock absorber as set forth in claim 5 in which each valve meanscomprises a stack of at least three superposed leaf elements, the leafelements being of graduated diameter with the largest one nearer theorifrees.

References Cited in the file of this patent UNITED STATES PATENTS2,467,098 Rossman Apr. 12, 1949 2,670,814 Ball Mar. 2, 1954 2,673,625Crabtree Mar. 30, 1954 2,676,676 Strauss et al. Apr. 27, 1954 2,748,898De Carbon June 5, 1956

